Field of Art
The present disclosure relates to an ophthalmic apparatus, a system and a method for controlling an ophthalmic apparatus.
Description of the Related Art
An ophthalmoscope is an apparatus for gathering information about the interior portion of an eye (fundus). A simple direct view ophthalmoscope is a handheld device used by an optician to directly view the fundus which may include a light source, an aperture, and one or more lenses. An electronic ophthalmoscope uses one or more sensors to obtain fundus images. These fundus images are then displayed to the optician with a display device. High resolution ophthalmoscope may use lasers to obtain high resolution fundus images. High resolution ophthalmoscope may also include adaptive optics to obtain even higher resolution fundus images. The adaptive optics can be used to compensate for the static and dynamic distortions introduced by the eye being examined. Examples of ophthalmoscopes include: ophthalmic image pickup apparatuses; fundus imaging systems; scanning laser ophthalmoscopes (SLO); adaptive optics scanning laser ophthalmoscope (AO-SLO); optical coherence tomographs (OCT); that utilize the interference of low coherence light; adaptive optics optical coherence tomographs (AO-OCT); etc. These ophthalmoscopes are important tools for the study of the human fundus in both normal and diseased eyes.
In AO-SLO and AO-OCT the adaptive optics (AO) are an optical correction system that measures the aberration of the eye and corrects for the measured aberration. The AO-SLO and AO-OCT may measure the wavefront of the eye using a Shack-Hartmann wavefront sensor system. A deformable mirror or a spatial-phase modulator is then driven to correct for the measured wavefront, and an image of the fundus is acquired, thus allowing AO-SLO and AO-OCT to acquire high-resolution images.
Eye movement is a big issue for imaging using these systems. A SLO may take multiple images for averaging and constructing panoramic images. In order to properly construct these images, each image should be in an exact position. This can be difficult because the eye moves continuously during imaging. Especially, on small FOV (Field Of View) systems such as AO-SLO eye movement can be quite large relative to the frame size. Sometimes the imaging area can go out of frame due solely to the eye movement.
In order to address this problem, eye position tracking systems are used. An eye position tracking system estimates an eye position using a position detection apparatus and shifts the imaging area according to the estimated eye movement using one or more tracking mirrors or by adjusting the scanning mirrors. The position detection apparatus may use image based position calculation methods that include detecting specific features or by analysis of the image as a whole.
There are a plurality of imaging techniques that may be used to image the eye using an AO-SLO or an AO-OCT. These include, confocal imaging, dark field imaging, fluorescence imaging, multispectral imaging, non-confocal imaging, split detection imaging, etc. An imaging apparatus may be designed to use multiple imaging techniques simultaneously. While this provides more information for diagnosis and investigation, it also present challenges for an image based tracking system. The plurality of images can produce conflicting tracking information.
What is needed is an apparatus and method of handling image based eye tracking with multiple sometimes conflicting tracking information.